1. Field of the Invention
This invention relates to a new and useful improvement in synthesizing a large pore crystalline composition from a specific new reaction mixture containing cyclohexylamine as directing agent and a source of oxide of a +3 valance element X, e.g., aluminum, and at least one of i) a source of oxide of a +4 valence element Z, e.g., silicon and ii) a source of oxide of a +5 valence element Y, e.g. phosphorus.
More particularly, this invention relates to an improved method for preparing a crystalline large pore composition whereby synthesis is facilitated and reproducible and the product comprises crystals having large pore windows measuring greater than about 10 Angstroms in diameter, such as, for example, greater than about 12 Angstroms in diameter. In one particularly preferred embodiment, alkoxides are used as the source of +3 valence element oxide and/or +4 valence element oxide.
2. Discussion of the Prior Art
Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversion. Certain zeolitic materials are ordered, porous crystalline aluminosilicates having a definite crystalline structure as determined by X-ray diffraction, within which there are a large number of smaller cavities which may be interconnected by a number of still smaller channels or pores. These cavities and pores are uniform in size within a specific zeolitic material. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as "molecular sieves" and are utilized in a variety of ways to take advantage of these properties.
Such molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline aluminosilicates. These aluminosilicates can be described as rigid three-dimensional frameworks of SiO.sub.4 and AlO.sub.4 in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total aluminum and silicon atoms to oxygen atoms is 1:2. The electrovalence of the tetrahedra containing aluminum is balanced by the inclusion in the crystal of a cation, for example an alkali metal or an alkaline earth metal cation. This can be expressed wherein the ratio of aluminum to the number of various cations, such as Ca/2, Sr/2, Na, K or Li, is equal to unity. One type of cation may be exchanged either entirely or partially with another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange, it has been possible to vary the properties of a given aluminosilicate by suitable selection of the cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.
Prior art techniques have resulted in the formation of a great variety of synthetic zeolites. The zeolites have come to be designated by letter or other convenient symbols, as illustrated by zeolite A (U.S. Pat. No. 2,882,243), zeolite X (U.S. Pat. No. 2,882,244), zeolite Y (U.S. Pat. No. 3,130,007), zeolite ZK-5 (U.S. Pat. No. 3,247,195), zeolite ZK-4 (U.S. Pat. No. 3,314,752), zeolite ZSM-5 (U.S. Pat. No. 3,702,886), zeolite ZSM-11 (U.S. Pat. No. 3,709,979), zeolite ZSM-12 (U.S. Pat. No. 3,832,449), zeolite ZSM-20 (U.S. Pat. No. 3,972,983), zeolite ZSM-35 (U.S. Pat. No. 4,016,245), zeolite ZSM-38 (U.S. Pat. No. 4,046,859), and zeolite ZSM-23 (U.S. Pat. No. 4,076,842) merely to name a few.
Aluminum phosphates are taught in U.S. Pat. Nos. 4,310,440 and 4,385,994, for example. These aluminum phosphate materials have essentially electroneutral lattices. U.S. Pat. No. 3,801,704 teaches an aluminum phosphate treated in a certain way to impart acidity. U.S. Pat. No. 4,673,559 teaches numerous different silicoaluminophosphate structures. Examples 17 and 18 of that patent show synthesis of MCM-9, a silicoaluminophosphate composition containing crystals having large pore windows measuring between 12 and 13 Angstroms in diameter.
U.S. Pat. No. No. 4,880,611 teaches compositions which comprise crystals having large pore windows of at least about 10 Angstroms, e.g., from about 12 to about 13 Angstroms, in diameter. An example of such a composition is a large pore crystalline [metallo]aluminophosphate which has a framework topology after heating at 110.degree. C. or higher giving an X-ray diffraction pattern with interplanar d-spacings at 16.4.+-.0.2 Angstroms, 8.2.+-.0.1 Angstroms, 6.21.+-.0.05 Angstroms, 6.17.+-.0.05 Angstroms, 5.48.+-.0.05 Angstroms and 4.74.+-.0.05 Angstroms, and without a significant interplanar d-spacing at 13.6-13.3 Angstroms. This material and its method of preparation are further set out in the aforementioned U.S. Pat. No. No. 4,880,611 which is incorporated herein by reference. Such a composition can be prepared from a reaction mixture hydrogel containing sources of aluminum oxide, phosphorus oxide, water, and a directing agent DA, preferably tetrapropylammonium.
An early reference to a hydrated aluminum phosphate which is crystalline until heated at about 110.degree. C., at which point it becomes amorphous or AlPO.sub.4 tridymite, is the "H.sub.1 " phase or hydrate of aluminum phosphate of F. d'Yvoire, Memoir Presented to the Chemical Society. No. 392, "Study of Aluminum Phosphate and Trivalent Iron", July 6, 1961 (received), pp. 1762-1776. This material, when crystalline, is identified by the Joint Commission for Powder Diffraction Standards (JCPDS), card number 15-274, and has an X-ray diffraction pattern exhibiting lines of Tables I and II, hereinafter presented. Once heated at about 110.degree. C., however, the d'Yvoire material becomes amorphous. The 18-membered ring aluminophosphate VPI-5 was published by M. Davis et al. at the "Innovation in Zeolite Materials Science" meeting in September, 1987. A further description of this material and its metal substituted aluminumphosphate counterparts can be found in published PCT application WO 89/ 01912, International Application Number PCT/US 88/02910 to Davis et al, filed 24 Aug. 1988 and published 9 Mar. 1989. U.S. Pat. No. 4,673,559 discloses the 18-membered ring silicoaluminophosphate MCM-9.
Silicoaluminophosphates of various structures are taught in U.S. Pat. No. 4,440,871. Aluminosilicates containing phosphorous, i.e. silico[metallo]aluminophosphates of particular structures are taught in U.S. Pat. Nos. 3,355,246 (i.e. ZK-21) and 3,791,964 (i.e. ZK-22). Other teachings of silicoaluminophosphates and their synthesis include U.S. Pat. Nos. 4,673,559 (two-phase synthesis method); 4,623,527 (MCM-10); 4,639,358 (MCM-1); 4,647,442 (MCM-2); 4,664,897 (MCM-4); 4,639,357 (MCM-5) and 4,632,811 (MCM-3).
A method for synthesizing crystalline metalloaluminophosphates is shown in U.S. Pat. No. 4,713,227, and an antimonophosphoaluminate and the method for its synthesis are taught in U.S. Pat. No. 4,619,818. U.S. Pat. No. 4,567,029 teaches metalloaluminophosphates, and titaniumaluminophosphate and the method for its synthesis are taught in U.S. Pat. No. 4,500,651.
The phosphorus-substituted zeolites of Canadian Patents 911,416; 911,417 and 911,418 are referred to as "aluminosilicophosphate" zeolites. Some of the phosphorus therein appears to be occluded, not structural.
U.S. Pat. No. 4,363,748 describes a combination of silica and aluminum-calcium-cerium phosphate as a low acid activity catalyst for oxidative dehydrogenation. Great Britain Patent 2,068,253 discloses a combination of silica and aluminum-calcium-tungsten phosphate as a low acid activity catalyst for oxidative dehydrogenation. U.S. Pat. No. 4,228,036 teaches an alumina-aluminum phosphate-silica matrix as an amorphous body to be mixed with zeolite for use as cracking catalyst. U.S. Pat. No. 3,213,035 teaches improving hardness of aluminosilicate catalysts by treatment with phosphoric acid. The catalysts are amorphous.
U.S. Pat. No. 2,876,266 describes an active silicophosphoric acid or salt phase of an amorphous material prepared by absorption of phosphoric acid by premolded silicates or aluminosilicates.
Other patents teaching aluminum phosphates include U.S. Pat. Nos. 4,365,095; 4,361,705; 4,222,896; 4,210,560; 4,179,358; 4,158,621; 4,071,471; 4,014,945; 3,904,550 and 3,697,550.
Lok et al., 3 Zeolites, 282-291, (1983), teach numerous organic compounds which act as directing agents for synthesis of various crystalline materials, such as, for example, ZSM-5, ZSM-11, ZSM-12, ZSM-20, ZSM-35, ZSM-48, AlPO.sub.4 -5, AlPO.sub.4 -8, AlPO.sub.4 -20 and others. The article does not show use of the presently required directing agent compound for synthesis of the large pore composition of this invention. However, Lok et al show that the synthesis of AlPO.sub.4 -5 and AlPO.sub.4 -17 are directed by cyclohexylamine and the use of aluminum isopropoxide to reduce crystallization rates in AlPO.sub.4 synthesis.
Metal alkoxides are shown in 63 J. Of Non-Crystalline Solids, 35 (1984) to improve homogeneity of certain non-crystalline gels. U.S. Pat. No. 4,440,871 to Lok et al, Examples 26 and 50 teach the preparation of SAPO-17 and SAPO-44, respectively, using aluminum isopropoxide as the aluminum source in the forming mixture and cyclohexylamine as templating agent with crystallization at 200.degree. C. Moreover, the above-mentioned PCT application WO 89/ 01912, International Application Number PCT/US 88/02910 to Davis et al, discloses the preparation of 18-membered ring large-pore AlPO.sub.4 material known as VPI-5, utilizing aluminum alkoxides.
U.S. application Ser. No. 07/636,054, to Chu et al., filed on even date herewith, discloses an improvement in calcining crystalline [metallo]aluminophosphate compositions by treatment with non-oxidizing gas followed by treatment with oxygen-containing gas at high flow rates, which avoids or minimizes structural changes during calcination which can be utilized with the method of the present invention.